Computers and computer networks are widely used by most all businesses to keep records, communicate, produce documents and otherwise manage information. Frequently, the work prepared on a computer is preferably rendered into hardcopy form so that it can be stored or sent to another party. For this reason, printers and other printing devices that can render hardcopy documents from computer data are critically important.
There are many different types of printers and printing devices. For example, types of printers include laser printers, inkjet printers, thermal printers, dot matrix printers and others. Printing devices may include plotters, copiers, facsimile machines, multi-function peripherals, etc. As used hereafter and in the appended claims, the term “printer” will be used to refer expansively to all printers and printing devices that output hardcopy documents.
FIG. 1 illustrates a generic printer and its hardware for performing basic and premium functions. In basic operation, the printer (100) receives print job data over a connection (110) with a host computer or computer network (not shown).
The print job data is received by a formatter (104). The formatter (104), which typically incorporates a microprocessor, related programmable memory and a page buffer, analyzes the incoming print job data and formulates and stores an electronic representation of each page that is to be printed. Once a page has been formatted, it is transmitted to the page buffer within the formatter. From the page buffer, the electronic data is fed systematically to the print controller (109).
The print controller (109) drives a print engine (101). The print engine (101) can be of various types depending on the type of printer (100). For example, the print engine may include a laser for a laser printer, an inkjet print head for an inkjet printer, etc. The print engine (101), under the control of the print controller (109) prints the data to a print medium, usually paper.
A print medium handling system will typically pull the paper from a supply tray (103). The paper is then routed (105) to the print engine (101) where printing occurs. The paper may then be transported (106) out of the printer (100) for collection by the printer user. This is the scenario for one-sided or simplex printing.
A typically premium function in printers is the ability to print on both sides of the paper or other print medium. Where this is the case, the paper, after having been printed on one side by the print engine (101) is transported (107) to a duplexing unit (102) rather than being transported (106) out of the printer (100).
The duplexing unit (102) turns and reorients the paper so that the second side of the paper can be printed on. The paper leaves the duplexing unit (102) and is transported (108) back to the print engine (101) where the second side of the paper is printed. Then the paper is transported (106) out of the printer (100) for collection by the user.